The present invention relates to disc brakes and more particularly to warning devices for indicating wear of friction pads.
In a known friction pad wear warning device or sensor, at least one projection is imbedded in a friction pad. When the pad is worn out to a predetermined thickness, the projection flushes with the pad surface. When the brakes are applied to a rotating disc, the projection rubs on the rotating disc at an area disposed within the contact surface of the pad and emits a high pitched squeal. This squeal is to alert the driver that something is wrong and he should take appropriate action. The problem with this known sensor resides in the difficulty to imbed the projection in the pad because the distance between a pad backing plate and the rotatable disc is limited. Another problem is that the contact surface of the pad on the rotating disc will be scratched and worn because the projection rubs on the rotating disc. Still another problem is that imbedding the projection into the pad will require digging a hole for receiving the projection and welding the projection to the bottom of the hole. Still another problem is that upon exchange of a worn-out pad, the associated projection must also be changed.